Elastic fiber laying die, laying device comprising such a die, and use of said device

ABSTRACT

A laying device ( 28 ) that is configured to lay fiber pieces ( 40, 40′, 40″ ) has a flexible surface ( 164 ) that applies and presses the fiber pieces against a preform surface.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a laying device for laying fiber pieces. Theinvention also relates to a laying die for use in the laying device. Thelaying device according to the invention is particularly suitable foruse in a process of manufacturing a preform for a load path alignedfiber composite structure.

At the construction of vehicles of all kinds, particularly at theconstruction of aircrafts and spacecrafts, but also in other branches ofindustry such as mechanical engineering, there is an increasing need forstrong and yet lightweight, cost-efficient materials. Especially fibercomposite materials offer an outstanding lightweight constructionpotential. The principle resides in the fact that particularlyhigh-strength and stiff fibers are embedded in a matrix in a load pathaligned fashion, thus producing components having outstanding mechanicalproperties by using previous techniques and having a weight which at acomparable performance is typically 25% less than that of aluminumstructures and 50% less than steel structures. A drawback is the highmaterial costs and particularly the laborious and mainly manualfabrication.

Accordingly, there is a desire for an automated manufacture facilitatingmachine positioning of the fibers in space.

To produce fiber composite structures with load path aligned fibers,so-called preforms as textile semi-products have been manufactured forselected applications. These are mostly two- or three-dimensionalstructures having a load path aligned fiber orientation. For thispurpose, endless fibers are laid in the direction of the load by usingdevices from textile engineering and are usually prefixed by sewing,knitting or similar techniques also performed with the aid of devicesfrom textile engineering. Examples of devices and processes formanufacturing such preforms are described in DE 30 03 666 A1, DE 196 24912, DE 197 26 831 A1 and DE 100 05 202 A1.

However, the known processes for manufacturing preforms are complicatedconcerning their implementation and process technique. Particularly forcomponents where curved load path lines with a varying density are to beexpected, it is not possible with previous processes to manufacture acorrespondingly load path aligned component. Particularly, the fiberscannot be oriented arbitrarily along defined curved paths and the fibercontent cannot be locally varied.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a device foruse in the manufacture of textile semi-products for load path alignedfiber composite structures with which the fibers can be better adjustedto complicated load paths.

This object is achieved by a laying device according to a first aspectof the invention.

A laying die for use in such a laying device and a beneficial use in aprocess for manufacturing fiber composite structures are the subject ofother aspects. Advantageous embodiments of the invention are the subjectof the other aspects.

According to the invention, a laying device for laying fiber pieces withan elastically deformable surface for pressing fiber pieces in atwo-dimensional fashion against a three-dimensional forming surface isprovided.

Such a device allows for example the placement of fiber pieces alongarbitrary surface geometries, for example even along three-dimensionalcurved surface structures.

In a process for manufacturing textile semi-products in which the layingdevice can be preferably employed, a preform can be produced in such away that first of all a bundle of fiber filaments, preferably a roving,is spread into a flat form. From this spread bundle of fiber filaments afiber band piece, in the following also referred to as a patch, is cutoff preferably in a predefined length. Thereafter the fiber band pieceis picked up and placed at a predefined position by means of a layingdevice. There the fiber piece is fixed by means of a binder material.The cutting, placement and fixing of fiber band pieces is repeated, withthe fiber band pieces being placed and fixed at different predefinedpositions. This preferably takes place in such a manner that the desiredpreform having a corresponding load path aligned fiber orientation isformed from several patches fixed adjacent to each other and/or topossible other component parts of the preform. Thus it is possible forexample to specifically reinforce also a part of a conventionallyfabricated preform, for example by placing patches in a load pathaligned fashion at positions which are particularly stressed.

Generally such a process, which cab also be referred to as a fiber patchpreforming technology, enables the placement of short fiber pieces(patches) at the precise position by a special laying process. Therequired properties of the preform can be obtained through theorientation and the number of fiber pieces.

The laying device according to the invention enables an orientation offiber pieces along complicated three-dimensionally curved surfaces.

In a preferred embodiment, the laying device is suitable within thescope of such a fiber patch preforming technology (FPP) to preciselyposition fiber pieces (patches) which are impregnated with a binder andare cut into predefined geometries according to a special layout. Alaying die which is proposed for this purpose forms a part of a layingdevice and can be used in different geometrical variations, for examplein the form of a square or in the faun of a roller etc.

The elastically deformable surface is preferably provided on anelastomeric body. Especially the flexible surface is preferably madefrom silicone, an elastomer, which is able to stand many load cycles andsimultaneously has a separating function that is beneficial especiallyin the transfer of binder-impregnated fibers and also for the placementof the fibers.

The adaption of the surface by means of an elastomeric body is similarto the pad printing technique, although any similar use in a layingdevice is not known.

In a preferred use of the laying device within the scope of themanufacture of preforms, load path aligned preforms can be producedespecially by the placement of spread, short-cut fiber pieces. A fibercutting system for instance cuts specially prefabricatedbinder-impregnated fiber bands into short pieces and delivers the sameto a vacuum band-conveyor where the fiber band pieces are separated andtransferred to the laying device. The delivery of the fiber band piecesto a laying head of the laying device takes place smoothly via acombination of suction modules and blow-off modules.

In a preferred embodiment, the laying device is provided with anactivation device for the binder material, for example with a heatingdevice on the laying head which heats the fiber band piece during itstransfer to the position where it is to be placed and thus activates thebinder. The laying head presses the fiber band piece onto the predefinedposition and then moves away preferably by a blow-off pulse. Thereafter,the laying head returns to its initial position.

For producing even complicated three-dimensional architectures, it isprovided for example that during the placement the fiber band piece ispressed onto a section of a forming surface for the preform.

A laying head of the laying device including the flexible surface orpressing surface is preferably fully automatically controlled in such amanner that it can be reciprocated between at least one or more pickuppositions where the fiber pieces are picked up, for example individualones of the aforementioned fiber band pieces, and the respectivepredetermined positions.

To precisely place the fiber band pieces at the intended position, it isfurther preferred that the fiber pieces are held against the flexiblesurface. This can be implemented preferably by pneumatic forces,especially by means of a suction and blow-off operation. Holding thefiber band pieces by means of pneumatic suction has the advantage thatthe fiber pieces in addition to the simplified pickup can rest flatly onthe surface without distortions. Particularly in a case where the fiberband piece to be placed is in a flat, spread condition, the fiber bandpiece can be easily held by suction.

In a case where a positioning device, by which the flexible surface ismoved for the placement operation, is additionally provided with meansfor rotating or pivoting the surface, fiber pieces can be placed in aneasy way with mutually different fiber orientations thus enabling aplacement operation with fiber orientations able to follow even morestrongly curved predetermined paths.

Accordingly, in a preferred embodiment, the laying device is adapted fora fast and smooth pickup of fiber pieces such as fiber cuttings andtheir transfer to a defined placement position. During the transfer anactivation device activates a binder material for fixing the fibers. Aheater which is integrated for example in the contact surface heats thematerial and thus activates a binder present on the fiber cutting.

At its placement position, the fiber piece is pressed onto the surfaceof for example a preform where the flexible surface adjusts to thesurface geometry.

Further, at the placement position, the fiber group that has beenapplied in this way is advantageously released by a blow-off pulse. Thisalso contributes to cooling the binder material. The binder material iscooled at the placement position and becomes solid thus fixing thefibers. The fiber material remains at the placement position while thelaying head returns to the pickup position to pick up the next fiberpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described in more detail by way ofthe attached drawings wherein it is shown by:

FIG. 1 is a schematic overview of a device for manufacturing a preformfor producing load path aligned fiber composite structures;

FIG. 1 a is a schematic view of an alternative embodiment of the deviceof FIG. 1 at a separation plane indicated by a chain line;

FIG. 2 is a schematic view of a pay-off device employed in a deviceaccording to FIG. 1 for paying off a bundle of fiber filaments processedin the device according to FIG. 1;

FIG. 3 is a schematic perspective view of a position sensor for use in apay-off device of FIG. 2 and its characteristic curve;

FIG. 4 is a perspective view of a spreading device for explaining theprinciple of operation of the spreading of a bundle of fiber filamentsapplied in a device according to FIG. 1;

FIG. 5 is a schematic perspective view of a spreading device for use ina device according to FIG. 1;

FIG. 6 a is a schematic lateral view of a loosening device for use in adevice according to FIG. 1;

FIG. 6 b is a schematic illustration of the principle of operation ofthe loosening device of FIG. 6 a;

FIG. 7 is a schematic lateral view of a binder impregnation device foruse in a device according to a first aspect of the invention;

FIG. 8 is a schematic lateral view of a combination of a cutting andlaying device employed in one embodiment of a device for manufacturing apreform;

FIGS. 9 and 10 are schematic illustrations of the principle of operationof the cutting device of FIG. 8;

FIG. 11 is a schematic view of predetermined paths for the placement offibers by one of the devices according to FIG. 1 or FIG. 8;

FIG. 12 is a series of fiber band pieces placed by the device accordingto FIG. 1;

FIG. 13 is a schematic view of a preform to be manufactured in a deviceaccording to FIG. 1 or FIG. 8;

FIG. 14 is a schematic cross sectional view of a laying head for use ina laying device according to FIG. 1 or FIG. 8;

FIG. 15 is a bottom view of the laying head of FIG. 14; and

FIG. 16 is a detailed schematic perspective view of the laying device ofFIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an overall representation of a preform manufacturing devicegenerally designated by reference number 10. This preform manufacturingdevice allows the fabrication of a complicated textile semi-product withload path aligned fiber filaments for manufacturing fiber compositestructures in an easy manner even if the semi-product has a complicatedstructure. Such textile semi-products are called preforms. Theproduction of these preforms takes place in the device according to FIG.1 from binder-fixed individual short fiber pieces that were previouslycut off from a specially pretreated bundle of fiber filaments or fiberband. Accordingly, the preform manufacturing device can be divided upinto a preparation module 12 for preparing the fiber band 14 and acutting and laying module 16 for cutting off and placing fiber bandpieces. The dash-and-dot line indicates a possible separation 15 betweenthese modules 12 and 16.

FIG. 1 illustrates a first embodiment of such a cutting and layingmodule 16; a second embodiment of such a cutting and laying module 16 isillustrated in FIG. 8.

First of all the overall structure and the principle of operation of thepreform manufacturing device 10 are explained with reference to FIG. 1.Thereafter the individual modules will be described with reference tothe additional figures.

As can be seen from FIG. 1, the preform manufacturing device 10 includesa pay-off device 18, a spreading device 20, a binder impregnation device22, a cutting device 24, a transfer device 26, a laying device 28 and apreform 30. These individual devices 18, 20, 22, 24, 26, 28 and 30 caneach work independently and can also be used to serve their intendedpurpose without the respective other devices. The present disclosurehence comprises the respective devices 12, 16, 18, 20, 22, 24, 26, 28,30 individually and alone.

The pay-off device 18 serves to supply a fiber filament strand, forexample a roving 32. As described in more detail in the following, thepay-off device 18 is constructed in a manner such that the rovings 32can be paid off without twisting. For manufacturing carbon fiberreinforced (CFC) components, a carbon roving is used in the illustratedembodiment.

The spreading device 20 serves to spread the individual filaments of therovings 32 as widely as possible, to provide a fiber band 14 as flat aspossible from a number as small as possible of layers of individualfilaments placed side by side. For this purpose the spreading device 20includes a spreading installation 34 and a loosening installation 36 aswill be explained in more detail further down.

The binder impregnation device 22 serves to provide filaments of thefiber band 14 and/or individual fiber band pieces thereof with a bindermaterial 38 serving to fix the fiber band pieces in the preform. In theembodiment illustrated in FIG. 1, the binder impregnation device 22forms a part of the preparation module 12 and is thus used to providethe spread fiber band 14 with binder material 38. In embodiments of thepreform manufacturing device 10 which are not further illustrated, abinder impregnation device 22 can be additionally or alternativelyassociated to the cutting and laying module 16 to then provide the fiberband pieces already cut off with binder material 38.

The cutting device 24 is constructed for cutting off pieces of a definedlength from the fiber band 14 (fiber pieces). In the following theindividual fiber band pieces are referred to as patches 40, 40′, 40″.

The transfer device 26 serves to separate the patches 40 and to transferthe same to the laying device 28.

The laying device 28 is constructed in such a way that it can pick upindividual patches 40 and place them at predefined positions, in thepresent case on the preform 30. The preform 30 serves to give apredetermined three-dimensional surface design to the preform 42.

The preform manufacturing device 10 further includes a control device 44comprising several controls 44 a, 44 b. The control device 44 controlsthe individual devices or installations 12, 18, 20, 22, 26, 30 in amanner such that the preform 42 is formed from the individual patches 40in the manner of a patchwork quilt.

Accordingly, the preform manufacturing device 10 allows the followingprocess of manufacturing a preform 42 for a load path aligned fibercomposite structure being carried out automatically:

First of all a bundle of fiber filaments present in the form of a roving32 is spread and provided with the binder material 38 which in thepresent embodiment can be thermally activated. The binder-impregnatedfiber band 14 thus prepared is thereafter cut into pieces of a definedlength—patches 40. The patches 40 are separated and transferred to thelaying device 28. The laying device 28 places each patch 40 at arespectively predefined position 46 on the preform 30, and presses thepatch 40 onto the preform 30.

Accordingly, with this preform manufacturing device 10 a fiber patchpreforming technology can be implemented which allows the exactpositioning of short fiber pieces through a special laying process. Therequired properties of the preform 42 can be achieved through theorientation and the number of fiber pieces. It is thus possible toorient fibers along defined curved paths and the fiber content canlocally vary.

By the placement of spread, short-cut fiber band pieces—patches40—optimally load path aligned preforms 42 can be fabricated. A fibercutting device 48 cuts the specially prefabricated binder-impregnatedfiber bands 14 into short pieces and delivers the same to a vacuumband-conveyor 50 of the transfer device 26.

The delivery of the patches 40 from the vacuum band-conveyor 50 to alaying head 52 of the laying device 28 takes place smoothly through acombination of suction and blow-off modules. The laying head 52 heatsthe patch 40 during the transfer to its placement position and thusactivates the binder material 38. The laying head 52 presses the patch40 onto the predefined position and then moves away by a blow-off pulse.Thereafter the laying head 52 returns to the initial position.

This technology allows the fully automatic production of complex fiberpreforms. Parameters like fiber content, fiber orientation and curveradii can be largely varied.

In the embodiments illustrated herein, spread carbon fibers are usedinstead of textile semi-products for fabricating the preforms 42. Thelength of the fibers is very short (only a few centimeters) compared topre-fabricated layings using long fibers. By a specific positioning ofthe short fibers—in the patches 40—high mechanical characteristics canbe achieved which are similar to those of long fiber composites.

The short fibers can be relatively precisely placed along complex loadpaths. Textile cuttings as previously used for manufacturing suchpreforms merely allow preferential orientations being set. Thus with thetechnology herein described extreme geometric shapes can be produced.The manufacturing process is fully automated, and thickness variationswithin a preform and/or modified fiber volume contents can be achieved.

In the embodiment of the preform manufacturing device 10 illustrated inFIG. 1, a laser 54 is used as a fiber cutting tool 48 in the cutting andlaying module 16. The laser is process-controlled and is preciselymovable with respect to the fiber band 14. Further in FIG. 1, a robotarm is indicated as a mechanical laying system 184 for moving the layinghead. The preform 30 can be precisely moved and rotated in a definedfashion relative thereto, in order to produce complex 3D structures ofpreforms 42 in a simple way.

In summary, a principle of the embodiment of the fiber patch preformingtechnology herein described is based on spreading carbon fiber rovings32 as widely as possible, coating them with binder powder and cuttingthem into pieces of a defined length, so-called patches 40, by employinga novel cutting technique. These patches 40 are then picked up by aspecial laying device 28, placed at a predefined position and fixed bymeans of the binder material 38. In this way the most varying componentgeometries and fiber architectures can be produced.

In the illustrated fabrication process spread fibers are used. Fiberspreading forms a basis for avoiding local accumulations of fiber endswithin the later composite material, since the same cause stressconcentrations which in the worst case may result in a failure of thecomponent. Spreading reduces the thickness of the rovings 32. Thus morecontinuous fibers can reach the zone of influence of a fiber end andcompensate peaks of stress. Further, when the fibers are placed in anoverlapping fashion, the step or shoulder on the cutting end of a roving32 is reduced. In a non-spread roving such a step or shoulder could beas high as 250 μm and could cause a deflection of the carbon fibersituated on top of it from the load path direction. Additionally, a zonerich in resin could be formed there, negatively affecting the strengthof the material.

To carry out the spreading operation as effectively as possible,twisting of the roving 32 shall be avoided, since filaments runningtransversely could again constrict a spread roving. The tension withinthe roving 32 in its spread state should be constant, since thespreading width and the spreading quality could be influenced by tensiondifferences.

The pay-off device 18, which is described in more detail in thefollowing with reference to FIG. 2, serves to enable delivery of aroving 32 in a non-twisted state from a supply reel 56 and to compensatethe oscillating movement of the roving 32 during its withdrawal from thesupply reel 56. For this purpose the pay-off device 18 comprises amovable support 58 of the supply reel 56 which is so designed that thesupply reel 56 will correspondingly join up the position of the part ofthe roving 32 just being paid off, so that the pay-off position remainsas constant as possible.

For this purpose, the support 58 comprises a carriage 62 supported alonga linear guideway 60. The carriage 62 is movable by means of steppingmotors and, in the illustrated embodiment, by means of a drive screw 64in the direction of the rotation axis of the supply reel 56. Thecarriage 62 is driven by a motor 66 with an integrated control. A sensor68 monitors the current position 70 of the roving 32 and thus controlsthe rotation of the motor 66.

A photodiode 72 which is illustrated in FIG. 3 together with itscharacteristic curve serves as a sensor 68. A diode line of thephotodiode 72 registers the shadow of the roving 32 and outputs theposition via an amplifying circuit (not further shown) as an analogsignal. The center of a shadow corresponds to a particular voltage as afunction of the position. The analog signal is transmitted as a bipolartension signal to the control of the motor 66, with 0 Volt correspondingto the center of the sensor. Additionally, the sensor 68 is exposed to aflash from an IR-LED spotlight at a particular frequency, for example 10KHz, to prevent the measuring signal from being influenced by ambientlight. This sensor 68 is optimized for the special requirements of apay-off operation compensating the position of the roving 32 on thesupply reel 56 and also allows still further adjustments such as thedisplacement of the center and the adjustment of the bending. Thecombination of a spatial resolution photodiode 72 and a controlled servomotor 66 has the advantage that the counter movement is caused independence of the current speed of movement of the roving 32. Relativelylow-speed compensation movements are caused at low pay-off speeds,whereas high pay-off speeds cause correspondingly fast countermovements. This enables the roving 32 being unreeled mainlyoscillation-free as a flat band or tape 74. On the end of the pay-offdevice 18

the roving 32 passes in an S-like movement around two little reels 75—inthe present case two waisted stainless steel reels which additionallycalm final oscillations. Differently from the way illustrated in FIG. 1,the pay-off device 18 can also be operated completely autonomously, i.e.independently of the remaining modules and normally only requires powersupply, e.g. an electrical connection.

After the pay-off device 18 the roving 32 passes a spreading line in thespreading device 20.

As already mentioned above, the spreading device 20 comprises thespreading installation 34 which is shown in more detail in FIG. 5 andthe function principle thereof is described with reference to FIG. 4.

FIG. 4 shows the basic layout of a conventional spreading principlealready known from DE 715801 A. Here a fiber strand 14 successivelypasses a bent rod 76 and thereafter a straight rod 78. In theconventionally known radius spreaders illustrated in FIG. 4, thecombination of a straight rod and a bent rod provides for a pullingforce which acts on the fiber being redirected. Now also a force actsthrough which the fiber is pressed onto the bent rod. At the highestpoint of deflection the filaments are subject to the highest force. Thisforce decreases with an increasing distance from this point. This meansthat the filaments can evade the load if they move outwardly on the bentrod. But the result of the spreading operation depends on the pullingforce acting on the fiber, the friction between fiber and rod, theposition of the rods relative to each other and the curvature of therod. If the curvature is extreme, the difference of the forces actingbetween the highest point and an outward position is so big that thesurface friction of the rod does no longer play a part. The filamentswould abruptly move outwardly, i.e. the roving 32 would slip off orsplit. If the curvature is insufficient, the spreading ratio would betoo small.

For this reason, the radius spreader illustrated in FIG. 4 is notsuitable for the industrial processing of rovings 32 to prepare the samefor the preform fabrication on an industrial scale. In particular,defects in the roving 32 such as twisting, gaps or folds would cause thespread material to slip off or split.

With the spreading installation 34 illustrated in FIG. 5 the problemsconcerning the quality of the material of rovings or of other fiberfilament bundle intended to be spread, in that the roving 32 or thefiber filament bundle is newly placed again and again onto at least oneconvexly bent spreading edge. For this purpose the spreadinginstallation 34 includes at least one convexly curved spreading edge 80which moves relative to the roving 32 or any other bundle of fiberfilaments by at least one component direction perpendicular to thelongitudinal extension of the roving 32 or any other bundle of fiberfilaments, so that the same is placed under tension onto the convexlycurved spreading edge 80 and thereafter moves away vertically from theroving 32 or the bundle of fiber filaments by at least one directioncomponent, so that the bundle of fiber filaments becomes detached fromthe spreading edge 80.

In its practical configuration the at least one spreading edge 80 isformed on a radial projection 82 on a rotary shaft 84.

In the preferred construction according to the embodiment illustrated inFIG. 5, at least two edges, at least one of which being constructed as aconvexly curved spreading edge 80, is movable from opposite directionstowards the roving 32 or the bundle of fiber filaments. For this purposethis embodiment provides two rotary shafts 84, 86 having radialprojections 82. The rotary shafts 84, 86 rotate in mutually oppositedirections.

In addition to first radial projections 82, where the convexly curvedspreading edges 80 are formed, a preferred embodiment also providessecond radial projections 88 terminating in straight edges 90. Aspreading device is thus provided in which at least one convexly curvedspreading edge 80 and at least one straight spreading edge 90 can movefrom opposite directions towards the roving 32 or the bundle of fiberfilaments until the roving 32 or the bundle of fiber filaments is spreadbetween the edges 80, 90 in the manner similar to that illustrated inFIG. 4. The edges 80, 90 can also be returned in the opposite directionto relieve the roving 32 or the bundle of fiber filaments.

In the embodiment according to FIG. 5, this is particularly easilyimplemented in that several wings 94 forming the radial projections 82,88 are formed on the rotary shafts 84, 86 driven in the oppositedirections by means of a gear mechanism 92. The wings 94 substantiallyextend in the axial direction and the edges 80 or 90 are formed on theirradially outermost regions. A wing 94 comprising the straight edge 90 isfollowed in the circumferential direction by a wing comprising a convexradially outwardly curved spreading edge 80, and this wing is in turnfollowed by a wing 94 comprising a straight edge 90 and so on.

In a different embodiment, the edges of all wings 94 are constructed asradially outwardly curved spreading edges 80. By the arrangement onmoving elements that move in the opposite directions, in the presentembodiment the two rotary shafts 84, 86, the fibers are each spreadbetween two oppositely curved spreading edges 80.

In this way the spreading installation 34 is constructed as a so-calledwing-type spreader which provides for a repeated placement of therovings 32 on the spreading edges 80. Additionally, a finishing layer onthe roving 32 or on the bundle of fiber filaments is broken open by thealternating bending operation, and the filaments 100 can moveindependently from each other.

The spreading installation 34 in the spreading device 20 constructed asa wing-type spreader is followed in the conveying direction of therovings 32 by a loosening installation 36 which in the presentembodiment is constructed as a suction chamber according to theso-called Fukui principle. The suction chamber 96 can be of a type whichis described in U.S. Pat. No. 6,032,342. The loosened and pre-spreadroving 32 is drawn into the suction chamber 96 by a strong laminar airstream 98. Air is caused to flow around the individual filaments 100 sothat the filaments can relatively easily slide one above the other.Further the suction chamber 96 is able to compensate minor fluctuationsin the tension of the rovings 32.

At the production of plastic fibers the bundles of filaments arefrequently freely guided and passed through eyelets. During thisoperation, parts of the filaments 100 can twist around the remainder ofthe bundle and cause constrictions of the rovings already at the time ofmanufacture. After the reeling of the bundle of filaments on a rovingreel these defects are hardly visible, because the bundle of filamentsis reeled up in a flat condition. But after the bundles of filamentshave been loosened in the spreading installation 34 roving parts runningin the transverse direction can be clearly seen. This effect can causegaps and displacements within the roving 32 which negatively influencethe spreading quality.

To achieve a spreading pattern which is as homogeneous as possible, anembodiment of the invention which is not explicitly shown provides for amultistep spreading operation, in which the spreading ratio is stepwiseincreased. For this purpose a first spreading installation 34 and afirst loosening installation 36 for spreading the roving 32 to a firstwidth, for example a value between 8 and 16 mm, are provided. This isfollowed by a next step comprising a further spreading installation 34having a larger width and a further loosening installation 36 havinggreater dimensions than the first spreading installation and the firstloosening installation, in order to effect spreading to a larger width,for example to a value between 20 and 35 mm.

Thereafter, the roving 32 is present in form of a wide, thin band, i.e.the fiber band 14.

In the further process, this fiber band 14 is still provided with asmall amount of the binder material 38.

Theoretically, only three filaments are placed one on top of the otherin a 12 k roving which is 30 mm wide and perfectly spread. In this casea diameter of the filaments 100 of 7 μm and the highest packing densityhave been assumed. But in reality a roving 32 still includes spreadingdefects that may locally cause thicker areas and thus a higher number offilament ends.

The impregnation of the thus spread rovings 32 with binder material 38takes places in the binder impregnation device 22, the principle thereofis illustrated in FIG. 7. The basic principle of the binder impregnationdevice 22 is similar to that of a powder shaker of a kind described forexample in U.S. Pat. No. 3,518,810, U.S. Pat. No. 2,489,846, U.S. Pat.No. 2,394,657, U.S. Pat. No. 2,057,538 or U.S. Pat. No. 2,613,633.Accordingly, this powder shaker comprises a funnel 102 with a roller 106having radial raised portions 104 moving past the exit of the funnel.

In the illustrated embodiment said roller 106 is a knurled steel rollerwhich is transports the powder with its rough surface. This roller 106is in turn treated by a brushing roller 108 removing the powdery bindermaterial 38 from the roller 106 and sprinkling the same onto the fiberband 14 moving past under the roller 106.

Between the fiber band 14 and the application mechanism a voltage U canbe applied, so that the powder will electrostatically adhere to thefiber band 14 like in a powder coating process.

The transfer roller 106 and the brushing roller 108 are driven by twoseparate electric motors 110 and 112 to enable free adjustment of thesprinkling parameters. Control takes place through a control unit 114which can be a part of the control device 44.

To avoid the powder from becoming blocked thus causing jamming ofmachine parts, the funnel 102 is not rigidly fixed to the remainder ofthe binder impregnation device 22, but is supported on a holder 116which allows compensating movements. An advantage of the holder 116 isthat the funnel 102 can oscillate during operation thus automaticallyshaking the powder downwards. The powder is sprinkled in an amount whichcan be exactly dosed onto the surface of the roving 32 which moves pastunder the funnel at a defined speed of 3 to 6 m/min for example.Excessive powder falls into a collection container (not shown) outsideof the roving 32 and can be recycled to the process at a later time.

Measurements have shown that the amount of binder material applied bysprinkling is almost a linear function of the rotating speed of theroller 106.

The binder impregnation device 22 also includes a heating installation118 serving to fix the powder particles of the binder material 38melting at heating temperatures to the surface of the filaments 100.

In the illustrated embodiment the heating installation 118 comprises aheating line which is about 100 to 500 mm long. The preferred embodimentof the heating installation 118 is equipped with radiant heaters, in thepresent case infrared radiant heaters 120. The heating power of theheating installation 118 can be precisely set through the control unit114.

The binder particles are slightly melted and adhere to the fibersurface.

Thereafter—as illustrated in FIG. 1 a—the finished fiber band 14 can bereeled up on a special film reel 121 and stored for later use.

In the embodiment illustrated in FIG. 1, the fiber band 14 speciallyprefabricated in this way is supplied to the cutting installation whereit is cut into the patches 40, 40′, 40″ and thereafter laid by thelaying device 28.

FIG. 1 a shows an embodiment with separate modules 12, 16 and the use offilm reels 121 as an example for intermediate storage. The modules 12,16 in this form could also be situated in different production sites.

FIG. 8 illustrates in more detail a second embodiment of the cutting andlaying module 16. In the embodiment according to FIG. 8 the cuttingdevice 24 comprises a fiber cutting tool 122 having a knife system 124and a counter roller 126 and at least one or, as in the present case,several transport rollers 128.

The knife system 124 can be operated in dependence of the rotating speedof the counter roller 126 and/or the transport rollers 128, for cuttingpatches 40 of a defined length.

In particular, the knife system 124 includes a coupling mechanism (notfurther illustrated) coupling a drive unit of the knife system 124 withthe drive unit of the rollers 126, 128.

In the illustrated example the knife system 124 is provided with acutting cylinder 130 which, as a radial projection, includes at leastone and in the present case several cutting edges 132. In theillustrated embodiment the cutting cylinder 130 can be coupled by acoupling means not further shown to the drive unit of the counter roll126 in such a manner that the cutting edges 132 move with the sameperipheral speed as the surface of the counter roller 126.

The cutting device shown in FIG. 8 and in more detail in FIG. 9accordingly comprises a coupled cutting system 134 in which two pairs oftransport rollers 128 and a rubberized counter roller 126 are driven bymeans of a motor not further shown via a central form-lockingtransmission, for example a toothed belt (not shown). The transportrollers feed an endless fiber band—in the present case particularly thespread fiber band 14—and direct the same over the counter roller 126rotating at the same speed.

Above the counter roller 126 a cutter bar 136 is in the waitingposition.

If a cut is to be made, an electromagnetic clutch couples the cutter bar136 into the movement of the cutting system. At the contact point thecutter bar 136 and the counter roller 126 have the same rotating speed.The material to be cut is broken by a knife blade 138. Thereafter thecutter bar 136 is decoupled and stopped for example by means of anelectromagnetic brake (not shown). The second pair of transport rollers128 removes the cuttings.

The coupled cutting system 134 enables the cutting of spread fiber bandswithout distortion. The cutting act or the cutting length can beadjusted computer-controlled during operation.

The brake system (not explicitly shown) provides for a permanent lockingof the cutting cylinder 130 when the clutch is not active. The couplingand braking operations take place via a common changeover relay (notshown) thus excluding failure caused by program errors. A sensor system(not further shown), for example an inductive proximity switch,registers the position of the knife and provides for a braking effect onthe knives in a horizontal position. If the connected control unit, forexample the control unit 44, outputs a cutting command, the cuttingcylinder 130 is coupled, accelerates and makes a cut. If at this timethe cutting cylinder 130 has the same peripheral speed as the counterroller 126, as provided in this embodiment, the knife blade 138 is notbent or deformed resulting in an endurance of the knife which is muchhigher than that of a simple vertical knife. After the cutting operationthe cutting cylinder 130 is decoupled and decelerated and held at thesame position as at the beginning. The cutting length is programmed incontrol software.

FIG. 10 schematically illustrates the flow of the cutting systemcontrol. As shown in FIG. 10, the cutting cycle is predetermined independence of the feeding speed of the cutting system. The minimumcutting length results from the dimension of the cutting cylinder 130and the counter roller 126 and is within a range for example of thewidth of the spread fiber band 14. The maximum cutting length istheoretically unlimited.

In both illustrated embodiments of the cutting and laying module 16,after leaving the cutting device 24, the patches 40, 40′, 40″ aretransferred to the transfer device 26 which removes the patches 40, 40′,40″ from the cutting device 24 at a transporting speed which is higherthan the conveying speed of the fiber band 14 to the or in the cuttingdevice 24. Thus the patches 40, 40′, 40″ are separated and sufficientlyspaced from each other. The transfer device 26 comprises a holdingsystem to hold the patches 40, 40′, 40″ fast to the transfer device anda delivery system to deliver the patches 40, 40′, 40″ to the laying head52 of the laying device 28.

The holding system and the delivery system are here implemented in theform of a vacuum band-conveyor 50. A large-volume suction chamber 140distributes the suction force of a vacuum source not further shown, forinstance a suction blower, over the entire transfer device 26. A bandcomprising many through pores, for example a polypropylene band, ispassed over a perforated metal sheet 142 covering the suction chamber140.

The transfer device 26 is driven through its coupling to a conveyor unitof the cutting device 24. In the illustrated embodiment, the vacuumband-conveyor 50 is coupled to the form-locking transmission driving thetransport rollers 128 and the counter roller 126. A correspondingtransmission ratio, e.g. a transmission ratio of 1:2, provides for asufficiently large distance between the patches 40, 40′, 40″. At the endof the transferring distance a suction-type blow-off chamber 144 issituated and driven by a pneumatic vacuum module. The suction-typeblow-off chamber is in operation as long as a fiber piece—patch 40—ispassed over the suction-type blow-off chamber 144. As soon as the layingdie is at a predetermined delivery position 146, a blow-off pulse isoutput at the right moment to deliver the patch 40 to the laying head52.

The laying head 52 attracts the patch 40 by suction, heats and transfersit with a predetermined orientation to its predetermined position.

As illustrated in FIG. 11, during this operation the patches 40, 40′,40″ are placed onto the preform 30 along predetermined curved paths 148.Pos. 150 indicates patches laid with a corresponding orientation alongthese curved paths 148 and their overlapping. In the overlapping zonesthe patches 40 are fixed to each other by the binder material 38 heatedby the laying head 52.

The cutting device shown in FIG. 1, in conjunction with a laser 54 (orany other kind of beam cutting technique) even allows the production ofcomplicated shapes of cutting edges. FIG. 12 illustrates a particularlypreferred shape of cutting edges, with the cutting edges 152, 154 beingcurved in a complementary fashion convexly or concavely with respect toeach other. The oppositely directed cutting edges 152, 154 on each patchare curved in a circular arc fashion. Thus the cutting edges 152, 154 ofpatches 40, 40′, 40″ that are arranged one behind the other can beplaced very close to each other without producing gaps or thickeningseven if the patches 40, 40′, 40″ are angled. In this way a lay-up ispossible with the fiber pieces constantly tightly abutting and having acorresponding fiber orientation also along small curvature radii of thepaths 148. The fixing of the patches 40, 40′, 40″ can be effected byoverlapping with adjacent patches or those arranged above or underneath(not shown).

In this manner it is possible to produce even very complicated preforms42 like those indicated for example in FIG. 13. In this example, shortfiber pieces according to the patchwork type make up a preform 192 for aload path aligned fiber composite structure for a window funnel of anaircraft or spacecraft for example. The patches 40, 40′, 40″ areoriented corresponding to the load paths.

Concerning the technical process, the illustrated annular shape can beachieved by defined rotatable preform 30 as indicated by the arrows 156in FIG. 1.

Now, the laying device 28 and its laying head 52 of the embodiment ofthe cutting and laying module 16 illustrated in more detail in FIG. 8will be further explained with reference to the FIGS. 14 to 16.

The laying head 52 has the function to pick up a fiber piece or patch40, 40′, 40″ and to transfer the same to the respective nextpredetermined position 46 on the preform 30 requiring lay-up of a patch40, 40′, 40″. For this purpose the laying head 52 includes a holdingdevice. While other holding devices are also conceivable, the holdingdevice in the illustrated example is constituted by a suction device 158which makes picking up the patches from the transfer device 26 easier.

Further, it is advantageous to activate the binder material 38 withwhich the picked-up patch 40 is provided, during the transfer by meansof the laying head 52. For this purpose the laying head 52 includes anactivation system for activating the binder material 38. Theconfiguration of the activation system depends on the binder materialwhich is used. For example, if a binder material is used which isactivated by an additive, the laying head comprises means for adding theadditive. In a different embodiment not further illustrated, aninstantly activated binder material such as an adhesive is supplied onlyduring the transfer of the patch on the laying head. In this case thelaying head includes means for the addition of binder material. For usein the above-described preform manufacturing device employing athermally activated binder material 38, the activation system isconstructed as a heating device 160 in the illustrated embodiment.

It is further preferable for the laying head 152 being able to lay-upthe patch 40, 40′, 40″ even against complicated three-dimensionalsurface architectures of the perform 30. To this end, the laying head 52includes a pressing device 162 suitable for pressing the transferredpatches 40 against different surface architectures. The pressing device162 includes in a preferred construction a flexible surface 164 wherethe patch 40 can be held by means of a holding device. Furtherpreferably, the flexible surface 164 is formed on an elastic carrier166.

FIG. 14 shows a cross sectional view of a laying die 168 of the layinghead 52 combining the holding device, the activation system and thepressing device. The laying die 168 shown in FIG. 14 accordinglycomprises the suction device 158, the heating device 160 and thepressing device 162 with the flexible surface 164 on the elastic carrier166.

FIG. 15 is a bottom view of the flexible surface 164.

If the fiber patch preforming technology (FPP) is applied, the layingdie 168 enables fiber pieces (patches) which are binder-impregnated andcut into defined geometries being precisely placed at the intendedposition according to a laying pattern (for example the laying patternshown in FIG. 11). The laying die 168 is a central component of thelaying technology and can be used also in other geometrical variations.For example, square or roller-shaped laying dies are also conceivable.

In the concrete embodiment according to FIG. 14, the laying die 168 isconfigured as a silicone die. The surface adaption of the silicone dieis similar to pad printing, although the present field of application iscompletely different.

The laying head 168 can quickly and gently pick up and transfer fibercuttings to the defined location through an integrated suction—suctiondevice 158. During the transfer, a heater—heating device 160—integratedin the contact surface—flexible surface 164—heats up the material andthus activates the binder—binder material 38—on the fiber cutting. Thefiber cutting is pressed onto the surface, with the soft die materialadjusting to the surface geometry. When the laying die 168 moves awayfrom the surface, a blow-off pulse is output, the binder material 38 iscooled and the fiber material remains where it has been placed.

The laying die 168 enables the production of fiber patch preforms 42.

In FIG. 14, the elastic carrier 166—elastic pressing body—is representedincluding an air distribution 170 which forms a part of the suctiondevice 158. The part of the suction device 158 which is not illustratedis provided with the usual pneumatic sources and pneumatic controls (notshown). Further, the flexible surface 164 is represented as an elasticheating surface 172 including suction and blow-off channels 174.

The elastic carrier 166 is seated on a coupling plate 4 which isprovided with removable fixing elements (not shown) for fixing thelaying head 168 to a positioning device 176 (see FIG. 16).

Further, a thermo element 178 is provided as a control element of theheating device 160. A highly flexible electrical power line 180 connectsthe thermo element 178 to the elastic heating surface 172.

FIG. 15 shows a suction surface—flexible surface 164—including thesuction and blow-off channels 174.

The use of the laying die 168 as well as further details of the layingdevice 28 will be described in the following in context with its use inthe preform manufacturing device 10.

In the fiber patch preforming technology individual fiber patches 40 arearranged to form a three-dimensional preform 42, 192. To achieve this,the layout plan is implemented by applying a suitable laying technique.The laying device 28 is delivered the binder-impregnated and cut fiberpatches 40 from the vacuum band-conveyor 50 associated with the cuttingdevice 24 and places the fiber patches 40 onto a surface, at a cyclewhich is a quick as possible. In the illustrated embodiment the fiberpatches 40,40′, 40″ are placed onto a surface of the preform 30.

The patches 40, 40′, 40″ shall be pressed onto the forming surface toproduce a robust preform 42. The laying die 168 shall be as soft aspossible to adjust to a three-dimensional surface with uniform force.For this configuration it is further preferred that shortly before theplacement of the patches a certain amount of heat can be provided foractivating the binder material 38. For this purpose the flexible surface164 includes the heating device 160 which influences the mechanicalproperties of the die material as less as possible. Similar to thevacuum band-conveyor 50, a two-dimensional fixing of the filigree fiberpatches 40 is beneficial. For this purpose the flexible surface 164 alsohas a suction function.

The manufacture of the laying die 168 is similar to the manufacture ofprinting pads known from printing engineering. For the manufacture ofprinting pads a series of special silicones are available which are ableto resist for a long time the permanent mechanical load cycles. Amongthese silicones this kind of silicone is selected which meets theadditional requirements caused by the heating device 160 and the contactwith the binder material 38 as perfectly as possible. For example thesilicone type M 4615 available on the market from the company of Wackeris suitable because of its high tensile strength and its ability to bedoped with softeners. Since the laying die 168 has incorporated aheater, tests have been made with regard to the temperature stability ofthe die material. In this case it is advantageous for the laying die 168being able to resist permanent temperatures of up to 200° C.Conventional softeners based on silicone oil have a tendency to anincreased diffusion and may leak from the silicone die. This problem canbe solved by softeners by which the silicone has at least partly beenwetted. Such a softener is available for example from the company ofWacker under the product name MH20.

For heating the lay-up surface of the laying die 168 various heatingdevices 160 can be used, among others also electric heating devices,fluid circuits or hot air. Concerning the fabrication technique, thevariant comprising an electric heating device 160 is the most convenientto implement and simultaneously offers the possibility of a high heatingpower and an exact temperature setting.

To not influence the flexibility of the carrier 166, the electric powerlines 180 are advantageously formed by means of carbon fiber yarn. Thehigh flexibility of such a fiber yarn prevents the flexible surface 164from becoming stiff. Also, such a fiber is able to stand several 100,000load cycles.

The thermal conductivity of the elastic carrier 166 can be increased byadmixing then sally conductive material to the silicone. Aluminum powderor a powder of any other light metal is suitable for this purpose.

With a powder moiety of about 10-25 percent by weight, particularly 20percent by weight, the thermal conductivity of the flexible surface 164is sufficiently high, so that a heating element of the heating device160 and the flexible surface 164 can be kept at almost the sametemperature.

On the other hand, a higher powder moiety might affect the flexibilityof the laying die 168. If the powder moiety is still further increased,an electrical breakdown may be caused. For this reason, the statedmoiety is the most preferred moiety.

The suction and blow-off channels 174 are integrated in the flexiblesurface 164 of the laying die 168 and join each other inside the layingdie 168 through a chamber 182. In the chamber 168 an absorbing suctionfleece (not shown) is inserted preventing collapsing when subject to thepressure load of the laying die 168.

To avoid electrostatic charging, the flexible surface 164 isadvantageously made of a flexible material having antistatic properties.The flexible surface is formed for example from an antistatic silicone.Thus the elastic carrier 166 formed from the above-mentioned siliconeexhibits good elastic properties while the flexible surface 164 isformed from an antistatic silicone. One example of such an antistaticsilicone is that available on the market under the trade name ElastosilRT402.

The mechanical lay-up system of the laying device 28 will still beexplained in the following with reference to FIG. 16.

The mechanical lay-up system 184 illustrated in FIG. 16 serves to movethe laying die 168, in order to transfer fiber patches 40 from thecutting device 24 to the predefined position 46. The mechanical lay-upsystem 184 allows a rapid laying cycle and an adjustable lay-up angle.

As explained above, the patch 40 is delivered in contactless fashionfrom the vacuum band-conveyor 50 to the laying die 168. For this purposethe control device 44 outputs a blow-off pulse of the suction/blow-offchamber 144 of the vacuum band-conveyor 50 after a preset delay time andin dependence of the cutting command. The patch 40 is delivered via anair path of a few millimeters (about 0.5-10 mm) to the aspiring layingdie 168. Thereafter, the movement cycle of the mechanical lay-up system184 commences.

The mechanical lay-up system 184 comprises a translational drive for thetransfer of the laying die 168 from the pick-up position to a positionabove the predetermined position. In the illustrated embodiment of themechanical lay-up system 184 the first drive unit is constituted by ahorizontal pneumatic cylinder 186. This horizontal pneumatic cylinder186 is adapted to move the laying die 168 from its pick-up position tothe placement position. A second drive unit constituted by a verticalpneumatic cylinder 188 presses the laying die 168 onto the surface,preferably at a pressure that can be adjusted.

During the displacement, the surface of the die is permanently kept atan adjustable temperature, so that the binder can activate itsadhesiveness. As soon as the patch 40 contacts the surface the bindermaterial 38 cools down and becomes solid. Then, under the control of thecontrol device 44, the blow-off pulse in the suction device of thelaying die 168 is output causing the laying die to move away andthereafter return to its initial position. Here the separatingproperties of the silicone are beneficial, because there is not anybinder material 38 remaining on the die.

By means of a third drive unit, which in the illustrated embodiment isconstituted by a stepping motor 190 including a spline shaft system 191,the laying die 168 can be rotated. Accordingly it is possible to evenproduce traces of inclined patches 40 without requiring the entirelaying head (e.g. the laying die 168 including the mechanical lay-upsystem 184) being rotated.

To achieve an economic laying process a very high cycle time of morethan two laying operations per second has been planned. Five layingoperations per second or even more are performed for example. With apatch length of 60 mm and using a 12 k roving, a fiber throughput oftheoretically 14.4 g/min is achieved. If it is intended for instance tocover one square meter with fiber patches 40 having the thickness of abiaxial laying (approximately 500 g/m²), the preform manufacturingdevice 10 would require 35 minutes. Shorter times are possible by usingseveral laying devices 28 in conjunction with several robots workingtogether on one surface.

Because of the relatively low achievable speeds, the FPP technique inits currently presented form is still mainly applied for thereinforcement of other types of preforms and for thin-walled and complexcomponents, for example the reinforcement of the rims of holes inmulti-axial layings or fabrics. A window funnel, the preform 192 thereofis shown in FIG. 13, could also be produced with a very thin wall andwith a defined fiber layer.

Certain types of preforms require less degrees of freedom in a FPPsystem—preform manufacturing device 10. If it is only reinforcementprofiles that are to be produced, the individual modules could besimplified and combined into one production line. Modules which are notrequired could be omitted. Alternatively, the device could be separatedin several modules including intermediate storage of the semi-finishedmaterial.

This would help to reduce system costs and to increase productivity.

1. A laying device configured to lay fiber pieces comprising: anelastically deformable surface being to press fiber pieces in atwo-dimensional fashion against a curved forming surface.
 2. The layingdevice according to claim 1, further comprising a laying head, whereinthe elastically deformable surface is arranged on the laying head, thelaying head is movable between at least one pickup position pick up atleast one fiber piece and at least one predetermined position to placethe picked up at least one fiber piece.
 3. The laying device accordingto claim 1, further comprising a holding device that holds a fiber piecein a releasable fashion against the elastically deformable surface. 4.The laying device according to claim 3, wherein the holding deviceincludes a pneumatic system by which the fiber piece is configured to bedrawn against and/or blown off the elastically deformable.
 5. The layingdevice according to claim 1, further comprising an activation devicethat activates a binder material to fix the fiber piece at a placementposition.
 6. The laying device according to claim 1, further comprisinga heating device that heats one of the fiber pieces applied against theflexible surface.
 7. The laying device according to claim 6, furthercomprising at least one flexible electric power line, wherein theheating device is configured as an electric heating device, the at leastone flexible electric power line electrically connects the heatingdevice.
 8. The laying device according to claim 1, wherein theelastically deformable is formed on an elastic carrier.
 9. The layingdevice according to claim 8, wherein the at least one electric powerline includes at least one carbon yarn passed through the carrier. 10.The laying device according to claim 8, wherein the elastic carrierincludes a block from an elastomer.
 11. The laying device according toclaim 1, wherein the elastically deformable is formed from an elastomer.12. The laying device according to claim 10, wherein the elastomer ismade from silicone.
 13. The laying device according to claim 12, whereinthe silicone is netted with a softener.
 14. The laying device accordingto claim 10, wherein metal portions are admixed to the elastomer. 15.The laying device according to claim 14, wherein the elastomer containsat least in the region of the flexible surface 10 to 25 percent byweight of light metal powder.
 16. The laying device according to claim1, wherein the elastically deformable is formed from or with anantistatic silicone.
 17. The laying device according to claim 10,further comprising at least one electric heating element that isembedded in the elastomer.
 18. The laying device according to claim 8,further comprising a holding device that holds a fiber piece in areleasable fashion against the elastically deformable surface, theholding device includes a pneumatic system by which the fiber piece isconfigured to be drawn against and/or blown off the elasticallydeformable surface, wherein the carrier has at least one channel thatconducts a pressure medium of the pneumatic device to the flexiblesurface and/or with a distribution system that distributes the pressuremedium over the flexible surface.
 19. The laying device according toclaim 18, wherein the channel or distribution system has at least onehollow space that has a gas-permeable supporting structure that uses asuction fleece.
 20. The laying device according to claim 1, wherein theflexible surface is provided with suction and blow-off channels toattract and blow-off a fiber piece.
 21. The laying device according toclaim 1, further comprising a positioning device moves and positions theflexible surface between at least two predetermined positions.
 22. Thelaying device according to claim 21, wherein the positioning device isadapted to rotate and to pivot the flexible surface about a rotary shaftthat intersects the flexible surface or intersects a plane that isparallel to this surface.
 23. The laying device according to claim 21,wherein a laying die that supports the flexible surface is mountable tothe positioning device.
 24. The laying device according to claim 23,wherein the laying die includes a coupling device to couple releasablythe laying die to the positioning device.
 25. The laying deviceaccording to claim 23, wherein the positioning device includes amechanical lay-up system that has a first drive unit that drives thelaying die in a first direction and a second drive unit that drives thelaying die in a second direction different from and approximatelyperpendicular to the first direction and a robot arm.
 26. A laying dieconfigured to be used in the laying device according to claim 1,comprising: a flexible surface; and a holding device being configured tohold a fiber piece against the flexible surface.
 27. A method of using alaying device comprising: preparing a laying device having anelastically deformable surface being configured to press fiber pieces ina two-dimensional fashion against a curved forming surface; andmanufacturing load path aligned fiber composite structures for theplacement of individual fiber cuttings at predetermined positions.